Control apparatus



Oct. 5, 1943. w, GILLE ET AL 2,331,183

CONTROL APPARATUS Filed April 15, 1942 TEMPERATURE RE5PQN5\VE as RE\STANCE.

Will-L5 111611112.

John \I'. 51'. fora. Leslie HZ. M1 1am INVENTORS A i fornqq PatentedGet. 5, 1943 CONTROL APPARATUS Willis H. Gille, St. Paul, and John V.Sigiord and Leslie H. Miller, Minneapolis, Minn, assignors toMinneapolis-Honeywell Regulator Company, Minneapolis, Minn, acorporation of Delaware Application April 13, 1942, Serial No. 438,800

15 Claims.

The present invention relates to sensitive relay mechanisms, andparticularly to sensitive relay mechanisms which perform a controlfunction in accordance with the position of a galvanometer needle orother sensitive measuring element.

An object of the present invention is to provide an improved mechanicalrelay mechanism of the type disclosed in the co-pending application ofWillis H. Gille, Serial No. 409,523, filed September 4, 1941. l

A further object of the invention is to provide a sensitive relaymechanism in which the dimensions of the parts are not critical, and inwhich accurate machining of the parts is therefore unnecessary.

A further object of the invention is to provide, in a sensitive relaymechanism including a cam and a follower member to be accuratelypositioned thereby, a motion reducing linkage between the cam and itsultimate follower, so that the manufacturing tolerances for the cam maybe greater than the allowable error in the positlon of the ultimatefollower.

A further object of the present invention is to construct a sensitiverelay mechanism wherein a control member is positioned periodically bybeing moved into engagement with a clamped galvanometer needle, andwherein the control member is unbiased. A still further object is toconstruct such a mechanism including slip friction means associated withthe control member for preventin the transmission of distorting forcesto the galvanometer needlel Other objects and advantages of my inventionwill become apparent alter a consideration of the accompanyingspecification, claims, and drawing, in which:

Figure 1 illustrates, somewhat diagrammatically, a control systemembodying my invention,

Figure 2 is a view looking from the rear of an operating assemblyconstituting an essential part of the mechanism shown in Figure 1, and

Figure 3 illustrates a detail of the mechanism shown in Figure l. I

"Figure 1 shows a system for controlling the temperature of a space 10.A radiator H is provided to heat the space i0, and steam or otherheating fluid is delivered to the radiator ll through a supply pipe l2.A valve l3 connected in the pipe 12 controls the supply of heating fluidto the radiator H. A resistance element [4, of nickel or some othersuitable substance having an appreciable temperature coeificient orresistance, is mounted in the space It. The resistance element [4 andthe valve [3 are interconnected by the control system in such a mannerthat the position of the valve I3 is determined by the resistance oi theelement i i.

The valve ii is positioned by means of a stem l5 rigidly connected to arack l6 which coopcrates with a motor driven pinion H.

The temperature responsive resistance element I4 is connected to abridge circuit generally indicated at 20, having input terminals 2| and22 and output terminals 23 and 24. The input circuit of the bridge 20connects terminals 2| and 22 and comprises a conductor 25, a battery orother suitable source of electrical energy 26, and a conductor 21.

The upper left-hand arm of the bridge 20, as it appears in the drawing,connects output terminal 23 with input terminal 2i and includes aconductor 30, a variable resistance 3i, a conductor 32, a fixedresistance 33 and a conductor 34. Variable resistance 39 serves toadjust the value of temperature in space ill at which bridge 20 isbalanced, for a given position of valve l3.

The upper right-hand arm of the bridge circuit 20 connects inputterminal 2! with output terminal 24 and includes a conductor 35,temperature responsive resistance element it, a conductor 36, and thatportion of a slidewire resistance $0 between a terminal 4! and the pointof engagement of a slider 42 with the slidewire 49. The output terminal24 is the point of engagement referred to. The slider t? is rigidlyattached to the stem I5 of the valve l3, and its position along theslidewire. 40 serves as a measure of the valve position.

The lower right hand arm of the bridge circuit 20 connects outputterminal 24 with input terminal 22, and includes that portion ofslidewire resistance ill between output terminal 24 and a terminal 43, aconductor 44, a fixed resistance 45, and a conductor E5.

The lower left-hand arm of the bridge circuit 20, asit appears in thedrawings, connects input terminal 22 with output terminal 23, andincludes a. conductor 50, a fixed resistance 5i, and a conductor 52.

The output circuit of bridge 29 connects output terminals 23 and E i,and includes a conductor 53, the moving coil 55 of a galvanometergenerally indicated at 55, a conductor 56, and the slider 42. Thegalvanometer 55 includes a permanent magnet 51 between whose poles thecoil 54 is rotatably mounted and a pointer 58 carried by the coil 54.

The pinion H is driven by a motor, generally indicated at 58, having arotor structure 8 l and a pair of opposed field windings '52 and 63. Therotor structure Si is connected to the pinion H through a motionreducing gea train generally indicated at 65. As indicated by the legendin the drawing, energization of motor field winding 62 causes rotationof rotor 6B in a direction opposite to that caused by energization offield winding $3. A pair of switches 65 and 86 control the energizationof windings 62 and 63. A sensitive relay mechanism is employed tocontrol the operation of switches E5 and 66 in accordance with theposition of the galvanometer pointer 58.

A. continuously rotating motor i drives, through a gear trainschematically indicated at H, a pair of rotary cams l2 and I3. Cam 12cooperates with a follower 14 mounted on one end of a pivoted lever 15so as to operate the lever 15 and periodically clamp the galvanometerneedle 58. Lever I is provided with an aperture '16 through which thepointer 58 passes. The aperture i6 is elongated to allow movement of thegalvanometer pointer 58 in response to unbalance of the bridge circuit26. Above the part of the pointer 58 which passes through the aperture16 is mounted a bar it.

The whole sensitive relay mechanism is supported on a suitable plate,diagrammatically indicated at 79. Lever i5 is supported by a pair offiat springs 80 and 8| attached to upstruck lugs on the lever it. Theother end of the flat springs 38 and 8| are attached to similar lugs ona bracket 82 adjustably mounted by means of a screw and slot connection83 on supporting plat 79. The spring 80 and 8| are so shaped that thecenter portion of spring 80 lies in front of and is spaced slightly fromthe center position of spring 8!.

The assembly consisting of bracket 82, springs and M, and lever 75 isconstructed with the springs unstressed, so that they take up a positionwhere their planes are mutually perpendicular, intersecting in a lineperpendicular to the plane of the drawing and passing through a pointfil on the bracket 82. This assembly is then mounted on the plate 79 bymean of the screw and slot connection 83 in such a manner that thesprings are forced out of their normal flat condition, and stressed justsufficiently to bias the lever 55 to provide the desired clampingpressure on the pointer 53 when follower i l is adjacent the low pointof cam l2.

This crossed spring pivot has no lost motion to be taken up when thelever clamps the pointer 58, such as is characteristic of moreconventional pivot structures. In a common pivot of the type where ashaft passes through a bearing, the shaft must be of smaller diameterthan the hole in the bearing in order to permit freedom of movement. Theshaft therefore moves at least slightly eccentrically with respect tothe bearing, and when a load is added to the shaft or bearin which actsas an angle to the previously existing load, a shift takes place in thepoint of contact of shaft and bearing. In a device of the type underconsideration, this shift in the bearing point would take place at themoment the pointer was clamped. Such a shift might permit slipping ofthe pointer after the initial engagement, with a resultant inaccuracy inthe operation of the device. While this difiiculty can be largelyovercome by careful dimensioning of the shaft and hearing, it should beremembered that one of the objects of this invention is to obviate thenecessity for such careful dimensioning.

The crossed spring pivot mechanism, which is well known in the art, isalso entirely frictionless. The force needed to rotate the lever may bedetermined from the characteristics of the springs '86 and 8!, and isnot subject to change because of friction at the pivot point.

As the cam 12 rotates, it engages the follower M and reciprocates thelever lie so that the aperture it is moved transversely to the path ofthe galvanometer pointer 58. As the right-hand end of lever 15approaches the upper limit of its reciprocating movement, the pointer 58is clamped between the lower edge of aperture it and'the lower edge ofthe bar ll. With the parts in the position shown in the drawing, thegalvanometer pointer 58 has just been clamped in that manner. When soclamped, the pointer 58 prevents further upward movement of theright-hand end of lever 15, so that the follower i i rides free of thecam 12, as shown in the drawing.

Cam is which rotates as a unit with cam 12, co-

operates with a follower 86 mounted on one end of a bell-crank lever 85,which is pivotally mounted as at 86 on a lever 90. Lever 90 is supportedby a pair of flat sp i 9i and Q2 attached to lugs on its lower end. Theother ends of the fiat springs 19f and 232 are attached to similar lugson a bracket 93 attached to a support is through an adjustable screw andslot connection 96. The flat spring members at and 52 not only supportthe lever 9b, but bias it so that the follower 86 is held in engagementwith the cam E3, the arrangement being generally similar to the pivotalsupport of lever 75 by the flat springs 88 and 8 i Bell-crank leverforms part of a motion reducing mechanism connecting cam 53 with lever98. The lower end 95 of the bell-crank lever 85 engages an adjustablestop 539 comprising a screw threadedly mounted on the lever so, andhaving aneccentric head. A brake lever 9b is ,pivotally supported on thelever 91!, as at all, and is provided with a shoe portion 93 adapted forengagement with a suitable surface on a switch operator N38. The switchoperator 4% is also plvotally mounted on the lever SE by a pin Hill. Atension spring 592 connects bell-crank lever 85 and brake lever 95. Thespring 32 has two functions. The first is to bias the bell-crank lever85 into engagement with the stop 98. The second is to bias brake lever95 so that the shoe portion 98 engages the switch operator AM.

From the foregoing description, it may be seen that the lever supportsand reciprocates an operating assembly whose chief elements are theoperator Hill, the bell-crank lever 35, and the brake lever 95. Figure 2shows a back view of this operating assembly, which may be compared withthe front view appearing in Figure 1. In Figure 2, it may be seen that ashoe piece N38 is riveted or otherwise suitably fastened to the back ofthe bell-crank lever 85. The shoe piece its has an arcuate surface H03.The surface its of the shoe piece N38 is adapted to engage a stop itmounted on a plate E05. The plate W5 is pivots ally attached to thesupporting plate '59 at I66 and is adjustable with respect to the platel9 by means of a screw and slot connection M11. The curvature of thesurface N13 is the same as that of the arcin which the stop Hl l movesas the plate 565 is rotated about its pivot point Hit. The function ofthe adjustable stop Hi l in cooperation with the shoe piece W2 is tochange the ratio by which the motion imparted to follower 8 3 by cam idis reduced during transmission to the lever 90. The exact mode ofoperation of these elements will be described in detail in connectionwith the description of the operation of the device as a whole.

Switch operator I carries at its upper end a long vertical extension H0which is adapted to engage galvanometer pointer 50. Switch operator W0is also provided, along its right-hand edge as it appears in Figure l,with a pair of lateral projections I II and I I2, which are adapted toengage and operate the switch members 55 and 63, respectively. The lowerend of operator I00 is provided with an arcuate surface H3, whose centerof curvature is the point IOI at which the operator I00 is pivoted. Thissurface H3 is adapted for engagement by the brake shoe 98. The surfaceH3 is provided with a groove H4 which is arcuate about center IM and anelongated spring member II5, attached to the plate I9, as at I I6, andis adapted to frictionally engage and ride in the groove H4. I

The pin IIlI extends rearwardly from the operator I00. An adjustablestop H1, comprising a screw having an eccentric head, threadedly engagesthe plate I9 so as to lie in the path of movement of the rearwardextension of pin Il0I.

A pin I8 is mounted on the cam 13 and serves to periodically engage theextremity of brake lever 96 and rotate it about its pivot 91 so as todisengage the brake shoe 98 from the'brake surface i I3 on the operatorI00.

Switch 65 comprises a stationary contact I20 and a movable contact I2I.Stationary contact I threadedly engages a bracket I22 attached to theplate 19. Movable contact I2I is supported at the end of a leaf sprinI23 whose opposite end is attached to a bracket I24 also supported onthe plate 19. The leaf spring I23 is self-biased so as to causeengagement of contact I2I with stationary contact I20. A. secondelongated spring member I25 is also attached to the bracket I24. Thespring member I25 is biased in opposition to the spring I23 and isprovided with a hole midway of its length so that the movable contactI2I can pass through it into engagement with contact I20. The relativeinitial tensions of springs I23 and I25 are such that they tend to takea neutral position wherein contacts I20 and I2I are separated. Thespring I25 is longer than the spring I23 and that portion of the springI25 which extends beyond contact I2I lies in the path of movement ofprojection III on the right-hand edge of switch operator I00. Asprojection III moves to the right in Figure 1, it engages the extremityof leaf spring I25 and carries it to the right away from leaf springI23. Leaf spring 523, being biased for movement to the right, followsthe spring I25 until contact I2I engages stationary contact i20. Afterengagement of contacts H0 and HI takes place, leaf spring I25 maycontinue to move to the right under the influence of projection Hi. Itshould be readily apparent, however, that this movement of leaf springi25 will not change the contact pressure between contacts I20 and I2I.The leaf spring 525 therefore serves as a strain release betweenoperator I00 and movable switch contact I2I.

Switch 56 is similar in construction to switch 65. It consists of astationary contact I and a movable contact I3I, Contact I30 isthreadedly mounted through a bracket I32 attached to plate "I9. ContactI3i is mounted on a leaf spring I33 attached to a second bracket I34. Astrain release leaf spring I35 cooperates with leaf spring I33 andprojection I92 of operator M0 in the same manner that strain releaseleaf spring I25 cooperates with leaf spring 523 and projection III inswitch 55. The brackets I and I34 are connected on the back of the plate19 by a suitable conductor strip I33 shown in dotted lines in thedrawing.

Motor I0 is provided with a winding I40 directly connected to powersupply lines HI and I42 by means of conductors I43 and I, respectively.A transformer I45 is provided having a primary winding I49 connected topower supply lines I and I42, and a secondary winding I", which suppliespower to the motor 50 through circuits to be hereinafter described indetail.

Operation With the parts in the positions shown in the drawing, thebridge circuit 20 is balanced. There is therefore no current flowing inthe bridge output circuit and the galvanometer pointer 58 is positionedin the center of its range of travel. The valve i3 is approximatelyhalf-way open, and the slider 42 is therefore approximately midwaybetween the terminals of the-slidewire 40.

Carn l2 has a portion 3i of constant radius followed by a drop-offportion 88, a slow rise portion 89 and a small hump I09. Cam l2 rotatesclockwise as indicated by the legend in the drawing. When the parts arein the position shown in the drawing, the follower I4 has just moveddown the drop-off portion 83, allowing the bias of flat spring membersand 8I.to swing the lever I5 in a counterclockwise direc tion, therebyclamping galvanometer pointer 56 between the lower edge of aperture 16and the lower edge of bar TI. 7

As the cam it continues to rotate clockwise, the slow rise portion 89engages follower 14, causing counter-clockwise movement of lever "I5 andcarrying the lower edge of aperture "I5 away from the galvanometerpointer 58. As the follower id moves over the hump I09, the upper edgeof aperture I6 comes down and engages the upper side of galvanometerpointer 58, thereby dislodging it from the edge of bar Ti in case it hasbecome stuck there. Follower I4 immediately moves back to the constantradius portion 87, so that the upper edge of aperture 16 is retractedbehind the bar 'I'I, freeing the pointer 58. The pointer remains free tomove within the aperture "I5 as long as the follower I4 rides onthedwell portion 81. When the follower 14 again moves down the dropoffportion 88, lever 75 is again moved counterclockwise, clamping thepointer 58 as previously described.

Cam I3 comprises a rise portion i552 followed by a rapid drop-offportion I5I, a slow drop off por tion I52, a very rapid drop-off portion553, and a low dwell portion H34. Cam '53 moves the follower 84 inaccordance with the variations of its contour. As previously noted, thebell-crank lever 85 carrying the follower 84 is biased by spring I02 sothat its lower end engages a stop 86, separating the lower end 95 oflever 85 from ment of lever 99 to that of follower St is determined bythe ratio of the distance between stop lu l and the pivot point 86 tothe distance be tween stop Hi l and follower M. It may readily be seenthat as stop Hi l approaches the position of pivot point 86, this ratiobecomes smaller, and therefore the reduction of movement betweenfollower 8% and lever 90 becomes greater.

The essential function of the assembly supported by the lever 96 is toalternately position the operator I in accordance with the position ofthe clamped galvanometer pointer 58 and then to move the positionedoperator I00 to the right into engagement with one or the other ofswitch contacts 55 and 56. The cam 73 is so proportioned that thisengagement of switch 65 or 66 takes place for a period of timeproportional to the deflection of the pointer 58 from its centerposition.

With the parts in the position shown in the drawing, follower 8 3 isjust about to move down the rapid drop-elf portion 153 of-cam 73,thereby allowing lever 90 to move rapidly to the left under theinfluence of springs 9i and 92. Just before the follower 8 3 moves downthe drop-off portion I53, the pin 18 engages the end of brake lever 96and rotates it counter-clockwise about the pivot Bl. This separatesbrake shoe 98 from the braking surface M3 on operator Hill. The operator188 is then free to move about its pivot ll)! restrained only by thefriction between spring tit and groove li i. As the lever Q0 movesrapidly to the left, the pivot IDI is moved with it. The lower end ofoperator lull is restrained however by friction between the spring vl l5and groove H6. Operator lilil therefore rolls along spring H6, rotatingin a counter-clockwise direction about the pivot fill. The long verticalextension N0 of operator lllii therefore moves to the left at a ratefaster than the leftward movement of lever 98. This rapid leftwardmovement of extension H6 continues until it engages the clampedgalvanometer pointer 58. Further movement of lever 90 to the left causesoperator Hill to rotate clockwise about the pivot Elli, and the springH5 slips along the groove ll i to permit this motion.

The position of adjustable stop H1 determines the limit of movement oflever 90 to the left. After the pin l0! engages stop ill, follower 8 3rides free of the cam 53. The effect of this is to make the finalposition of operator lilo dependent on pointer 58 and stop Ill, ratherthan on pointer 58 and low portion Hi l of cam l3. We have found thatthe position of stop ill can be determined with less error than theposition of the low dwell portion 73. The stop ill is used therefore tomake the device more accurate and less subject to errors of manufacture.

After the operator 100 is established at a position relative to thelever 90 which is determined by the position of the clamped galvanometerpointer 58, pin l8 moves out of engagement with brake lever 95. Thebrake lever 96 moves back to its normal position under the influence oftension spring m2, thereby engaging brake shoe 98 with the brakingsurface N3 of operator iilil and locking it in the position which hasbeen determined by the clamped pointer 58. When the operator Hill ismoved by lever 90 while it is locked by brake shoe 98, the spring H5slides freely in the groove il l.

As the follower 8% moves up the riser portion I58 of cam '13, lever 98is moved rapidly to the right until the stop 50% engages the surface I03attached to bell-crank lever 85. After this engagement takes place, themovement of lever 9b to the right continues but at a slower rate thanthe rate of rise of cam 53, as previously explained. Since thegalvanometer pointer i8 is clamped in its neutral position, the operatorHill is also set in a neutral position, and at the extreme limit of themovement to the right, both the projections Ill and H2 engage therespective fingers I and I35, but do not move either one sulficiently tooperate the switches 65 and 5B. As cam 13 continues to rotate, the lever9i! moves back to the left and the whole cycle of operation previouslydescribed is repeated.

It may now be seen that the purpose of the adjustable stop 9a is todetermine the point in the travel of lever 98 at which the motionreducing mechanism becomes effective. Adjustment of stop 99 changes thenormal angular position of bell-crank lever with respect to lever 90. Bynormal position is meant that position of lever 85 wherein its lower end95 engages stop 99. This normal angular position of lever 85 determinesthe spacing between surface Hi3 and stop lfll when the lever is in itsextreme left position. This spacing determines the distance throughwhich lever 98 moves to the right before the motion reducing mechanismbegins to function.

Now let it be assumed that the temperature in the space in decreasesbelow the value which the system has been set to maintain by adjustmentof variable resistance 3|. This decrease in temperature causes adecrease in the resistance of the temperature responsive element l 5,thereby causing an unbalance of the bridge circuit, in a manner wellknown in the art, so that a current flows in the bridge output circuitin a direction from output terminal 2 3 to output terminal 23. Thiscurrent flowing in the coil of galvanometer 55 causes a deflection ofpointer 58 to the left as viewed in the drawing. For the sake ofillustration, let it be assumed that the pointer 58 takes up a positionat the extreme left end of the aperure l6 and is clamped in thatposition by the lever 15. Then when the operator Hill is positioned byengagement of projection-H0 with pointer 58, it takes up a positionwhich is displaced counter-clockwise from the position shown in thedrawing. It is clamped inthis position by the brake S6, and when thelever 90 moves again to the right, the projection III engage strainrelease spring I25 and causes engagement between contacts |20 and l2l.This completes an energizing circuit for Winding 6'2 of motor fill. Thiscircuit may be traced from the upper termiha] of transformer secondarywinding it] through a conductor ifiil, bracket i3 5, conductor I36,bracket I24, leaf spring i123, contacts l2! and i211, bracket I22, aconductor ifil, motor winding 52, and a conductor H32 tow'the lowerterminal of transformer secondary winding Ml. Energization of winding 62causes rotation of motor IS in such a direction as to drive the valve l3toward open position and move the slider 52 upwards along the slidewireiil. This movement 9,881,188 of slider 62 increases the portion ofresistor 66 connected in series with the temperature responsive elementI 6, andthereby tends to restore the resistance in that arm of thebridge to its normal value. At the same time, the resistance-in theadjacent arm of the bridge is reduced. Both of these effects tend torestore the bridge circuit to a condition of balance.

Energization of motor winding 62 continues periodically in accordancewith the reciprocation of lever 96 and the position of' galvanometerpointer 66. As soon as the bridge has been rebalanced, the pointer 66again moves to its center position, and on the next cycle 01' operation,the operator I66 operates neither of the switches 66 nor 66. The netresult 01' the operation of the system just described is to open thevalve I3 somewhat so that more steam is supplied to the radiator II tobring the temperature of the space I6 back to the value which it isdesired to maintain.

Now let it be assumed that the temperature in the space I6 increasesabove the value which the system has been set to maintain. This causesunbalance of the bridge circuit 26 in the opposite direction, andcurrent flows from output terminal 23 to the output terminal 26 throughthe coil 56 of galvanometer 65. This cause a deflection of pointer 56 tothe right from its normal position, and therefore when the operator I66is next set by the pointer 66, it takes up a position displacedclockwise with respect to lever 66 from a position shown in the drawing.When the operator I66 is moved to the right, it engages switch 66,thereby completing an energizing circuit for winding 63 of motor 66.This energizing circuit may be traced from the upper terminal ofsecondary winding I 61 through conductor I66, bracket I36, leaf springI33, contacts I66 and Ill, bracket I62, conductor I66, motor winding 66,and conductor I62 to the lower terminal of transformer secondary windingI61. Energization of winding 63 causes operation of motor 66 in such adirection as to close the valve I6 and move slider 42 downward along theslidewire 66. This motion continues periodically under control of thesensitive.

relay mechanism until the bridge circuit 26 is rebalanced through themotion of the slider 62 along the slidewire 46. At'this time the valveI6 will have been closed slightly so as to reduce this supply of heat tothe radiator II and allow the temperature of the space I6 to decrease tothe desired value.

It should be noted that the cam I3 moves the lever 66 rapidly to theright, and then slowly backward to the left. In this way, the time atwhich the projections III and H2 engage the switches 66 or 66 isdetermined solely by the contour of the cam I6 As the lever 66 movesslowly backward to the left, however, the time atwhich the projectionIII or II2 separatesfrom its asso.. ciated switch is determined by theposition of the operator I66 with respect to the lever 96. Therefore, itwill be seen that the length of time during which the motor winding 62or 63 is energized is determined by the amount which the galvanometerpointer 66 is deflected from its normal position.

If cam I3 were shaped so as to have a smooth drop between the high pointof rise I66 and the beginning of the steep drop-off I66, a constantratio would be maintained between galvanometer deflection and the lengthof the period of motor energization. It has been found desirable,however, in order to overcome the tendency of the control system toovershoot the balance point of the bridge circuit, to reduce the periodof motor energization in proportion to galvanometer deflection when thedeflection is small. This effect is achieved by shaping the cam I3 sothat it has a first rapid drop-off portion I5I followed by a position ofthe lever '66 must be accurately determined at all times in order tocontrol the energization period. To secure this desired result, accuratecutting of the cam I6 is necessary. By inserting the motion reducingmechanism between cam I3 and lever 66, we have made it possible toexaggerate the contour of the cam, so that inaccuracies due to errors inthe cam form have substantially no effect on the motion of the lever 96.

While we have disclosed a specific embodiment of our invention, othermodifications will readily occur to those skilled in the art, and itshould therefore be understood that the invention is limited only by thescope of the appended claims.

We claim as our invention;

1. In a sensitive relay mechanism, in combination, a member forperforming a control function, an operator for engaging said member soas to cause it to perform said control function, means for positioningsaid operator in accordance with a controlling condition, means forreciprocating said operator between said positioning means and saidcontrol member, said reciprocating means comprisin a cam and a followertherefor, said cam being proportioned so that the period of engagementbetween said operator and said member is a function of the operatorposition, and a motion reducing linkage between said follower and saidoperator.

2. In a sensitive relay mechanism, in combination, a member forperforming a control function, an operator for engaging said member soas to cause it to perform said control function,

a means for positioning said operator in accordance with a controllingcondition, means for reciprocating said operator between saidpositioning means and said control member so that the period ofengagement between said operator and said member is a function of theoperator position, said reciprocating means including a lever and apivotal connection for supporting said operator on said lever, astationary frame for supporting said lever, and a slip-frictionconnection between said frame and said operator for causing rotation ofsaid operator about said pivotal connection during reciprocation of saidlever.

3. In a sensitive relay mechanism, in combination, a.me'mber forperforming a control function, an operator for engaging said member soas to cause it to perform said control function, means for positioningsaid operator in accordance with a controlling condition, means forreciprocating said operator between said positioning means and saidcontrol-member, so that the period of engagement between said operatorand said member is a function of the operator position, saidreciprocating means including a lever and a pivotal connection forsupporting said operator on said lever, a stationary frame forsupportingsaid lever.

' a slip-frictionconnection between said frame and said operator forcausing rotation of said operator about said pivotal connection duringreciprocation of said lever, brake means for preventing rotation I ofsaid operator about-said pivotal connection, and means for applying saidbrake means after said operator has been positionedby said positioningmeans and releasing said brake means after the termination of saidperiod of engagement between said operator and said member.

4. In a sensitive relay mechanism. in combination, a member forperforming a control function, an operator for engaging said member soas to cause it to perform said control function, means for positioningsaid operator in accordance with a controlling condition, means for'reciprocating said operator between said positioning means and saidcontrol member, said recip rocating means comprising a pivoted lever forsupporting said operator and cam means for moving said supporting levera bell-crank lever pivotally mounted on said supporting lever, firststop means mounted on said supporting lever for Cooperation with one endof said bell-crank lever to limit its rotation about said pivotalmounting, follower means mounted on the other end of said bell-cranklever for cooperation with said cam, spring means biasing saidbell-crank lever so that one end engages said stop and said levers moveas a unit upon initial movement of said follower by'-said cam, andstationary stop meansfor engaging a portion of said bell-crank lever soas to limit its movement as a unit with said supporting lever, saidbell-crank lever ongaging said stationary stop after said initialmovement and thereafter rotating about said pivotal mounting andtransmitting to saidsupporting lever a movement less than the movementimparted to said follower by said cam.

5. In a sensitive relay mechanism, in combination, a member forperforming a control function, an operator for engaging said member soas to cause it to perform said control function, means for positioningsaid operator in accordance with a controlling condition, means forreciprocating said operator between said positioning means and saidcontrol member. said reciprocating means comprising a pivoted lever forsupporting said operator and cam means for moving said supporting lever,brake means for locking said operator against movement with'respect tosaid lever}motion-reducing mechanism between said cam and said levercomprising a bell-crank lever pivoted on said supporting lever andcarrying a follower for engaging said cam,

and spring means connecting said bell-crank le v r and said brake meansso as to bias said brake means into engagement with said operator and tobias said bell-crank lover into engagement with a stop on saidsupporting lever.

6. -In a sensitive relay mechanism, in enmbination, a member forperforming a control function an operator for engaging said member so asto cause it to perform said controL function, means for positioning saidoperator in accordance with a controlling condition, means forreciprocating said operator between said positioning means and saidcontrol member, said reciprocating means comprising, a cam and afollower therefor, said cam being proportioned so that the period ofengagement between said operator and said member is a function of theoperator position, and a motion reducing linkage between said followerand said operator, said motion rcducing linkage being effective toreduce movements of said operator'only' during that phase of operatorreciprocation which includes said period of engagement.

7.--In a sensitive relay mechanism, in combination, a member forperforming a control function, an operator for engaging said member soas to cause it to perform said control function, means for positioningsaid operator in accordance with a controlling condition, means forreciprocating said operator between said positioning means and saidcontrol member, said reciproeating means comprising a pivoted lever forsupporting said operator and cam means for moving said supporting lever,and motion-reducing mechanism between said cam and said lever includinga bell-crank lever pivoted onsaid supporting cam.

8. In a sensitive relay mechanism, in combination, a sensitive elementmovable in accordance with the magnitude of a variable condition,

an operator to be positioned in accordance with the position of saidsensitive element, said operator comprising a lever having one endadapted for engagement with said element, and means for moving saidoperator into engagement with said sensitive element withouttransmitting any appreciable force to said element, said meanscomprising a driving member pivotally attached to saidlever at anintermediate point thereon, and a slip-friction connection between astationary member and said lever on the opposite side of saidintermediate point from said one end.

9. In a sensitive relay mechanism, in combination, a member forperforming a control function, an operator for engaging said member soas to cause it to perform said control function, means for positioningsaid operator in accordance with a controlling condition, means forreciprocating said operator between said positioning means and saidcontrol member, said reciprocating means comprising, a cam and afollower therefor, said cam being proportioned so that the period ofengagement between said operator and said member is a function of theoperator position, a motion reducing linkage between said follower andsaid operator, and means for varying the extent by which said linkagereduces the motion of the operatorin comparison to the motion of thefollower.

10. In a sensitive relay mechanism, in combination, a member forperforming acontrol function, an operator for engaging said member so asto cause it to perform said control function, means for positioning saidoperator in accordance with a controlling condition, mean forreciprocating said operator between said positioning means and saidcontrol member, said reciprocating means comprising a pivoted lever forsup porting said operator and cam means for moving said supportinglever, a bell-crank lever pivotally mounted on said supporting lever,first stop means mounted on said supporting lever for 00- operation withone end of said bell-crank lever to limit its rotation about,saidpivotal mounting, follower means mounted on the other end of saidbell-crank lever for cooperation with said cam, spring means biasingsaid bell-crank lever so that one end engages said step and said leversmove as a unit upon initial movement of said follower by said cam,stationary stop means for engaging a portion of said bell-crank lever soas to limit its movement as a unit with said supporting lever,-

said bell-crank lever engaging said stationary stop after said initialmovement and thereafter rotating about said pivotal mounting andtransmitting to said supporting lever a movement less than the movementimparted to said follower by said cam, and means for adjusting saidstationary stop means so as to vary the ratio between the movement ofthe follower and the movement of the supporting lever.

11. In a sensitive relay mechanism, in combination, a member forperforming a control function, an operator for engaging said member soas to cause it to perform said control function, means for positioningsaid operator in accordance with a controlling condition, means forreciprocating said operator between said positioning means and saidcontrol member, said reciprocating means comprising a cam and a followertherefor, said cam being proportioned so that the period of engagementbetween said operator and said member is a function of the operatorposition, brake means biased to engage said operator, and meansoperating concurrently with said cam for releasing said brake means whensaid operator engages said positioning means.

12. In a sensitive relay mechanism, in combi nation, a member forperforming a control function, an operator for engaging said member soas to cause it to perform said control function, means for positioningsaid operator in accordance with a controlling condition, means forreciprocating said operator between said positioning means and saidcontrol member, said reciprocating means comprising, a cam and afollower therefor, said cam being proportioned so that the period ofengagement between said operator and said member is a function of theoperator position, a motion reducing linkage between said follower andsaid operator, and means for. determining the phase of operatorreciprocation during which said motion reducing linkage is efiective toreduce the movements of said operato 13. In a sensitive relay mechanism,in combination, a member for performing a control function, an operatorfor engaging said member so as to cause it to perform said controlfunction, means for positioning said operator in accordance with acontrolling condition, means for reciprocating said operator betweensaid positioning means and said control-member, said reciprocating meanscomprising, a cam and a follower therefor, said cam being proportionedso that the period of engagement between said operator and said memberis a function of the operator position, and stop means independent ofsaid cam for determining the limit of movement of said operator towardsaid positioning means.

14. In a sensitive relay mechanism, in combination, an element forperforming a control function, an operator member for engaging saidelement so as to cause it to perform said control said members having asubstantially cylindrical 7 surface portion, and an elongated springmounted at one end on the other of said members and positioned to engagesaid surface portion, said urface portion and spring cooperating whensaid braking means is released so that said surface portion rolls onsaid spring when said lever is moved relative to said stationary member,thereby causing rotation of said operator member with respect to saidlever, said spring sliding over said surface portion when said brakingmeans is applied to permit relative movement of said lever and saidstationary member while said operator 3 member remains fixed withrespect to said lever.

l5. In a sensitive relay mechanism, in combination, an element forperforming a control function, an operator member for engaging saidelement so as to cause it to perform said control function, means forpositioning said operator member in accordance with a controllingcondition, means for reciprocating said operator mem ber between saidpositioning means and said control element so that the period ofengagement between said operator member and said control element is afunction of the position of said operator member, said reciprocatingmeans including a lever and a pivotal connection for supporting saidoperator member on said lever, a stationery member for supporting saidlever, one of said members having a substantially cylindrical surfaceportion, and an elongated spring mounted on the other of said membersand positioned to engage said surface portion, said surface portion andspring cooperating so that said surface portion rolls on said springwhen said lever is moved relative to said stationary member, therebycausing. rotation of said operator member with respect to said lever.

WILLIS H. GILLE.

JOHN V. SIGFORD.

LESLIE H. MILLER.

